1. Technical Field
The present disclosure relates to surgical generators. More particularly, the present disclosure relates to a surgical generator and related method for mitigating overcurrent conditions.
2. Discussion of Related Art
Energy-based tissue treatment is well known in the art. Various types of energy (e.g., electrical, ultrasonic, microwave, cryogenic, heat, laser, etc.) are applied to tissue for surgical treatment. Electrosurgery involves application of high radio frequency electrical current, e.g., electrosurgical energy, to a surgical site to cut, ablate, coagulate, or seal tissue.
In bipolar electrosurgery, there are typically two electrodes disposed on a held-held instrument. One of the electrodes of the hand-held instrument functions as the active electrode and the other as the return electrode. The return electrode is placed in close proximity to the active electrode such that an electrical circuit is formed between the two electrodes (e.g., electrosurgical forceps). Bipolar electrosurgical techniques and instruments can be used to coagulate blood vessels or tissue, e.g., soft tissue structures, such as lung, brain, and intestine. By controlling the intensity, frequency, and duration of the electrosurgical energy applied between the electrodes and through the tissue, a surgeon can cauterize, coagulate, desiccate, seal, or simply reduce or slow bleeding of tissue. In order to achieve one of these desired surgical effects without causing unwanted charring of tissue at the surgical site or causing collateral damage to adjacent tissue from thermal spread, the output from the electrosurgical generator is controlled, such as power, waveform, voltage, current, pulse rate, etc.
In monopolar electrosurgery, the active electrode is typically disposed on the surgical instrument held by the surgeon, and a patient return pad having one or more return electrodes is placed remotely from the active electrode to carry the current back to the generator and safely disperse current applied by the active electrode. The return electrodes usually have a large patient-contact surface area to minimize tissue heating at that site. Heating is caused by high current densities that directly depend on the surface area. A larger surface contact area results in lower localized heat intensity. The size of the return electrodes are chosen based on assumptions of the maximum current utilized during a particular surgical procedure and the duty cycle (i.e., the percentage of time the generator is on).
Another type of energy-based treatment of tissue is microwave-energy based treatment. There are several types of microwave surgical instruments (i.e., microwave probes) in use, e.g., monopole, dipole, and helical. The monopole antenna probe consists of a single, elongated microwave conductor exposed at the end of the probe. A dielectric sleeve typically surrounds the monopole antenna probe. The second type of microwave probe commonly used is the dipole antenna probe, which consists of a coaxial construction having an inner conductor and an outer conductor with a dielectric junction separating a portion of the inner conductor. The inner conductor may be coupled to a portion corresponding to a first dipole-radiating portion, and a portion of the outer conductor may be coupled to a second dipole-radiating portion. The dipole radiating portions may be configured such that one radiating portion is located proximally of the dielectric junction and the other portion is located distally of the dielectric junction. In the monopole and dipole antenna probes, microwave energy generally radiates perpendicularly away from the axis of the conductor.